Four sector economy refers to which of the following?

Open Economy

The correct answer is option (4) : Open Economy

There are four basic macroeconomic sectors of an economy, namely, household, business, government and foreign. These sectors reflect four key macroeconomic functions and are responsible for four expenditures on gross domestic product (GDP). Each sector has a unique role to play in macroeconomic activity. This type of Economy known as open Economy.

This classification allows for the inclusion of international trade and financial transactions, distinguishing it from a closed economy where international trade is negligible or absent.